The 913fd is a little bigger profile and it is a low spin, but good launch fairway wood for people with high speed or trying too take spin out of their shots and most people prefer to hit this fairway wood off of a tee. Now the 913f, has a little smaller head than the 913fd and is the better choice if you need a fairway wood to hit off of the ground or to reach par 5's in two. So it pretty much narrows it down to if you need a fairway wood to use off the tee as a straight driving club or a fairway wood to hit off of the ground. Hope this helps.

Connor.

I tested the 913F today (15* with the Venom shaft) at Golf Galaxy and boy was it incredible.  The Fd is going to be more for workability and the F is more forgiving which is what I was told.  

I was hitting it consistent and LONG!  I have a 909 F2 15.5 and I don't hit it very well.  The 913F 15* I was hitting consistently 220-230!

Can't wait to put my order in with my pro!

I picked up a 913Fd on launch day.  15*, diamana blue 72 stiff.  I never had a 910 so I don't have it to compare to, but I will say hands down the 913Fd is the best fairway wood I've ever hit.  It's long, forgiving, and fantastic performance.  

If I had been in your position, and unable to buy it in a store, I would have ordered it without a second thought.  Knowing that my driver spin is on the higher side, the Fd was the right selection for me.  I understand there is no substitute for being able to try the club before you buy, but even given my short history with Titleist, they bend over backwards to make sure that you are happy with your purchase.  (Always a good thing.)

I hope this helps.  Best of luck to you here's hoping you find more fairways and greens.